Implanting defibrillators in patients with suspected arrhythmia can lead to complications like infections, device malfunction or even heart or blood vessel damage, so physicians would rather avoid the procedure if it’s not absolutely necessary. Using a new, noninvasive 3-D virtual heart assessment tool designed by researchers at Johns Hopkins, physicians may be able to better determine the risks and benefits associated with such an implant for individual patients.

"Our approach has the potential to radically change the process of risk assessment for sudden cardiac death and the patient selection for prophylactic defibrillator implantation," Natalia Trayanova, senior author of the study and professor of biomedical engineering at Johns Hopkins, told HCB News. "The approach could eliminate many unnecessary defibrillator implantations and their associated complications."

In the study, which was published yesterday in the online journal, Nature Communications, the research team demonstrated that the virtual heart tool leads to more accurate predictions than the current standard approach — blood pumping measurements.

The team made predictions using MR records of 41 patients who survived a heart attack and were left with damaged cardiac tissue, which raises their chances of getting arrhythmias. They wouldn’t know until after the study how accurate their predictions were.

They found that each of the patients had an ejection fraction of less than 35 percent, which is a measure of how much blood is being pumped out of the heart. Patients within that range usually receive implantable defibrillators, so all 41 patients got one.

The team then used the MR scans from before the patients received the defibrillator to build digital replicas of each of their hearts. They used computer-modeling techniques to add representations of the electrical processes in the cardiac cells and the communication among cells.

The resulting virtual-heart arrhythmia risk predictor (VARP) will allow physicians to assess the way electrical waves move through the patient’s heart and the impact of scar tissue left by an earlier heart attack. Those factors will help them better determine the risk of sudden cardiac arrest due to arrhythmia.

The VARP results were compared with the defibrillator patients’ results after implantation to evaluate how well the technology worked. The patients who tested positive for arrhythmia risk with VARP were four times more likely to develop arrhythmia than those who tested negative.

In addition, VARP predicted the arrhythmias four to five times better than the ejection fraction and other noninvasive and invasive clinical risk predictors.

VARP may also save the lives of patients with preserved pumping function who could also be at significant risk for sudden cardiac death, said Trayanova. They are generally not targeted for defibrillator therapy under the current clinical recommendations.

Going forward, the researchers plan to perform additional research that involves larger groups of heart patients.